Studies are continuing on the proliferative patterns of the polyploid tumor cells of the methylcholanthrene-induced autogenous rat sarcoma. This animal model has been chosen because it simulates some human solid tumors in its slow growth and in the slow and complex proliferation of its cells (J. Natl. Cancer Inst. 50:403, 1973). These investigations deal with the relationship of the DNA synthesis time to DNA and chromosome contents and replication during the period of DNA synthesis. In addition studies will be made of the effects of commonly employed anti-cancer drugs upon these phenomena. BIBLIOGRAPHIC REFERENCES: A New Approach for Determining the Distribution of S plus G2 Times in Polyploid Tumor Cell Populations. R.J. Sklarew, J. Hoffman and J. Post. 12th Annual Meeting of the Amer. Assn. Cancer Research, Toronto, Canada, May 4-8, 1976. Pr. Am. Assoc. Cancer Research 17: 84, 1976. The Relationship Between Chromosome Nos. and S plus G2 Cell Transit-Times in the Polyploid MCA-rat Sarcoma In Vitro. R.J. Sklarew, J. Hoffman and J. Post. Presented at the 27th Annual Meeting of the Tissue Culture Assn., Phila., Pa., June 7-10, 1976. In Vitro 12(4): 325, 1976.